When using data networks, like Internet, for transactions between parties, that want to exchange information, that want to buy goods, enjoy services or receive information and other parties offering those goods, services or information, one of the problems observed is the lack or secure and at the same time simple transaction methods. Secure systems, such as SET, SSL, etcetera exist, but are felt as being cumbersome to use, involving heavy message traffic, (complex) cryptographic procedures, and key management including key recovery.